.. highlightlang:: c
.. _object:
Object Protocol
===============
.. cfunction:: int PyObject_Print(PyObject *o, FILE *fp, int flags)
Print an object *o*, on file *fp*. Returns ``-1`` on error. The flags argument
is used to enable certain printing options. The only option currently supported
is :const:`Py_PRINT_RAW`; if given, the :func:`str` of the object is written
instead of the :func:`repr`.
.. cfunction:: int PyObject_HasAttr(PyObject *o, PyObject *attr_name)
Returns ``1`` if *o* has the attribute *attr_name*, and ``0`` otherwise. This
is equivalent to the Python expression ``hasattr(o, attr_name)``. This function
always succeeds.
.. cfunction:: int PyObject_HasAttrString(PyObject *o, const char *attr_name)
Returns ``1`` if *o* has the attribute *attr_name*, and ``0`` otherwise. This
is equivalent to the Python expression ``hasattr(o, attr_name)``. This function
always succeeds.
.. cfunction:: PyObject* PyObject_GetAttr(PyObject *o, PyObject *attr_name)
Retrieve an attribute named *attr_name* from object *o*. Returns the attribute
value on success, or *NULL* on failure. This is the equivalent of the Python
expression ``o.attr_name``.
.. cfunction:: PyObject* PyObject_GetAttrString(PyObject *o, const char *attr_name)
Retrieve an attribute named *attr_name* from object *o*. Returns the attribute
value on success, or *NULL* on failure. This is the equivalent of the Python
expression ``o.attr_name``.
.. cfunction:: int PyObject_SetAttr(PyObject *o, PyObject *attr_name, PyObject *v)
Set the value of the attribute named *attr_name*, for object *o*, to the value
*v*. Returns ``-1`` on failure. This is the equivalent of the Python statement
``o.attr_name = v``.
.. cfunction:: int PyObject_SetAttrString(PyObject *o, const char *attr_name, PyObject *v)
Set the value of the attribute named *attr_name*, for object *o*, to the value
*v*. Returns ``-1`` on failure. This is the equivalent of the Python statement
``o.attr_name = v``.
.. cfunction:: int PyObject_DelAttr(PyObject *o, PyObject *attr_name)
Delete attribute named *attr_name*, for object *o*. Returns ``-1`` on failure.
This is the equivalent of the Python statement ``del o.attr_name``.
.. cfunction:: int PyObject_DelAttrString(PyObject *o, const char *attr_name)
Delete attribute named *attr_name*, for object *o*. Returns ``-1`` on failure.
This is the equivalent of the Python statement ``del o.attr_name``.
.. cfunction:: PyObject* PyObject_RichCompare(PyObject *o1, PyObject *o2, int opid)
Compare the values of *o1* and *o2* using the operation specified by *opid*,
which must be one of :const:`Py_LT`, :const:`Py_LE`, :const:`Py_EQ`,
:const:`Py_NE`, :const:`Py_GT`, or :const:`Py_GE`, corresponding to ````, or ``>=`` respectively. This is the equivalent of
the Python expression ``o1 op o2``, where ``op`` is the operator corresponding
to *opid*. Returns the value of the comparison on success, or *NULL* on failure.
.. cfunction:: int PyObject_RichCompareBool(PyObject *o1, PyObject *o2, int opid)
Compare the values of *o1* and *o2* using the operation specified by *opid*,
which must be one of :const:`Py_LT`, :const:`Py_LE`, :const:`Py_EQ`,
:const:`Py_NE`, :const:`Py_GT`, or :const:`Py_GE`, corresponding to ````, or ``>=`` respectively. Returns ``-1`` on error,
``0`` if the result is false, ``1`` otherwise. This is the equivalent of the
Python expression ``o1 op o2``, where ``op`` is the operator corresponding to
*opid*.
.. cfunction:: PyObject* PyObject_Repr(PyObject *o)
.. index:: builtin: repr
Compute a string representation of object *o*. Returns the string
representation on success, *NULL* on failure. This is the equivalent of the
Python expression ``repr(o)``. Called by the :func:`repr` built-in function.
.. cfunction:: PyObject* PyObject_ASCII(PyObject *o)
.. index:: builtin: ascii
As :cfunc:`PyObject_Repr`, compute a string representation of object *o*, but
escape the non-ASCII characters in the string returned by
:cfunc:`PyObject_Repr` with ``\x``, ``\u`` or ``\U`` escapes. This generates
a string similar to that returned by :cfunc:`PyObject_Repr` in Python 2.
Called by the :func:`ascii` built-in function.
.. cfunction:: PyObject* PyObject_Str(PyObject *o)
.. index:: builtin: str
Compute a string representation of object *o*. Returns the string
representation on success, *NULL* on failure. This is the equivalent of the
Python expression ``str(o)``. Called by the :func:`str` built-in function
and, therefore, by the :func:`print` function.
.. cfunction:: PyObject* PyObject_Bytes(PyObject *o)
.. index:: builtin: bytes
Compute a bytes representation of object *o*. *NULL* is returned on failure
and a bytes object on success. This is equivalent to the Python expression
``bytes(o)``.
.. cfunction:: int PyObject_IsInstance(PyObject *inst, PyObject *cls)
Returns ``1`` if *inst* is an instance of the class *cls* or a subclass of
*cls*, or ``0`` if not. On error, returns ``-1`` and sets an exception. If
*cls* is a type object rather than a class object, :cfunc:`PyObject_IsInstance`
returns ``1`` if *inst* is of type *cls*. If *cls* is a tuple, the check will
be done against every entry in *cls*. The result will be ``1`` when at least one
of the checks returns ``1``, otherwise it will be ``0``. If *inst* is not a
class instance and *cls* is neither a type object, nor a class object, nor a
tuple, *inst* must have a :attr:`__class__` attribute --- the class relationship
of the value of that attribute with *cls* will be used to determine the result
of this function.
Subclass determination is done in a fairly straightforward way, but includes a
wrinkle that implementors of extensions to the class system may want to be aware
of. If :class:`A` and :class:`B` are class objects, :class:`B` is a subclass of
:class:`A` if it inherits from :class:`A` either directly or indirectly. If
either is not a class object, a more general mechanism is used to determine the
class relationship of the two objects. When testing if *B* is a subclass of
*A*, if *A* is *B*, :cfunc:`PyObject_IsSubclass` returns true. If *A* and *B*
are different objects, *B*'s :attr:`__bases__` attribute is searched in a
depth-first fashion for *A* --- the presence of the :attr:`__bases__` attribute
is considered sufficient for this determination.
.. cfunction:: int PyObject_IsSubclass(PyObject *derived, PyObject *cls)
Returns ``1`` if the class *derived* is identical to or derived from the class
*cls*, otherwise returns ``0``. In case of an error, returns ``-1``. If *cls*
is a tuple, the check will be done against every entry in *cls*. The result will
be ``1`` when at least one of the checks returns ``1``, otherwise it will be
``0``. If either *derived* or *cls* is not an actual class object (or tuple),
this function uses the generic algorithm described above.
.. cfunction:: int PyCallable_Check(PyObject *o)
Determine if the object *o* is callable. Return ``1`` if the object is callable
and ``0`` otherwise. This function always succeeds.
.. cfunction:: PyObject* PyObject_Call(PyObject *callable_object, PyObject *args, PyObject *kw)
Call a callable Python object *callable_object*, with arguments given by the
tuple *args*, and named arguments given by the dictionary *kw*. If no named
arguments are needed, *kw* may be *NULL*. *args* must not be *NULL*, use an
empty tuple if no arguments are needed. Returns the result of the call on
success, or *NULL* on failure. This is the equivalent of the Python expression
``callable_object(*args, **kw)``.
.. cfunction:: PyObject* PyObject_CallObject(PyObject *callable_object, PyObject *args)
Call a callable Python object *callable_object*, with arguments given by the
tuple *args*. If no arguments are needed, then *args* may be *NULL*. Returns
the result of the call on success, or *NULL* on failure. This is the equivalent
of the Python expression ``callable_object(*args)``.
.. cfunction:: PyObject* PyObject_CallFunction(PyObject *callable, char *format, ...)
Call a callable Python object *callable*, with a variable number of C arguments.
The C arguments are described using a :cfunc:`Py_BuildValue` style format
string. The format may be *NULL*, indicating that no arguments are provided.
Returns the result of the call on success, or *NULL* on failure. This is the
equivalent of the Python expression ``callable(*args)``. Note that if you only
pass :ctype:`PyObject \*` args, :cfunc:`PyObject_CallFunctionObjArgs` is a
faster alternative.
.. cfunction:: PyObject* PyObject_CallMethod(PyObject *o, char *method, char *format, ...)
Call the method named *method* of object *o* with a variable number of C
arguments. The C arguments are described by a :cfunc:`Py_BuildValue` format
string that should produce a tuple. The format may be *NULL*, indicating that
no arguments are provided. Returns the result of the call on success, or *NULL*
on failure. This is the equivalent of the Python expression ``o.method(args)``.
Note that if you only pass :ctype:`PyObject \*` args,
:cfunc:`PyObject_CallMethodObjArgs` is a faster alternative.
.. cfunction:: PyObject* PyObject_CallFunctionObjArgs(PyObject *callable, ..., NULL)
Call a callable Python object *callable*, with a variable number of
:ctype:`PyObject\*` arguments. The arguments are provided as a variable number
of parameters followed by *NULL*. Returns the result of the call on success, or
*NULL* on failure.
.. cfunction:: PyObject* PyObject_CallMethodObjArgs(PyObject *o, PyObject *name, ..., NULL)
Calls a method of the object *o*, where the name of the method is given as a
Python string object in *name*. It is called with a variable number of
:ctype:`PyObject\*` arguments. The arguments are provided as a variable number
of parameters followed by *NULL*. Returns the result of the call on success, or
*NULL* on failure.
.. cfunction:: long PyObject_Hash(PyObject *o)
.. index:: builtin: hash
Compute and return the hash value of an object *o*. On failure, return ``-1``.
This is the equivalent of the Python expression ``hash(o)``.
.. cfunction:: long PyObject_HashNotImplemented(PyObject *o)
Set a :exc:`TypeError` indicating that ``type(o)`` is not hashable and return ``-1``.
This function receives special treatment when stored in a ``tp_hash`` slot,
allowing a type to explicitly indicate to the interpreter that it is not
hashable.
.. cfunction:: int PyObject_IsTrue(PyObject *o)
Returns ``1`` if the object *o* is considered to be true, and ``0`` otherwise.
This is equivalent to the Python expression ``not not o``. On failure, return
``-1``.
.. cfunction:: int PyObject_Not(PyObject *o)
Returns ``0`` if the object *o* is considered to be true, and ``1`` otherwise.
This is equivalent to the Python expression ``not o``. On failure, return
``-1``.
.. cfunction:: PyObject* PyObject_Type(PyObject *o)
.. index:: builtin: type
When *o* is non-*NULL*, returns a type object corresponding to the object type
of object *o*. On failure, raises :exc:`SystemError` and returns *NULL*. This
is equivalent to the Python expression ``type(o)``. This function increments the
reference count of the return value. There's really no reason to use this
function instead of the common expression ``o->ob_type``, which returns a
pointer of type :ctype:`PyTypeObject\*`, except when the incremented reference
count is needed.
.. cfunction:: int PyObject_TypeCheck(PyObject *o, PyTypeObject *type)
Return true if the object *o* is of type *type* or a subtype of *type*. Both
parameters must be non-*NULL*.
.. cfunction:: Py_ssize_t PyObject_Length(PyObject *o)
Py_ssize_t PyObject_Size(PyObject *o)
.. index:: builtin: len
Return the length of object *o*. If the object *o* provides either the sequence
and mapping protocols, the sequence length is returned. On error, ``-1`` is
returned. This is the equivalent to the Python expression ``len(o)``.
.. cfunction:: PyObject* PyObject_GetItem(PyObject *o, PyObject *key)
Return element of *o* corresponding to the object *key* or *NULL* on failure.
This is the equivalent of the Python expression ``o[key]``.
.. cfunction:: int PyObject_SetItem(PyObject *o, PyObject *key, PyObject *v)
Map the object *key* to the value *v*. Returns ``-1`` on failure. This is the
equivalent of the Python statement ``o[key] = v``.
.. cfunction:: int PyObject_DelItem(PyObject *o, PyObject *key)
Delete the mapping for *key* from *o*. Returns ``-1`` on failure. This is the
equivalent of the Python statement ``del o[key]``.
.. cfunction:: PyObject* PyObject_Dir(PyObject *o)
This is equivalent to the Python expression ``dir(o)``, returning a (possibly
empty) list of strings appropriate for the object argument, or *NULL* if there
was an error. If the argument is *NULL*, this is like the Python ``dir()``,
returning the names of the current locals; in this case, if no execution frame
is active then *NULL* is returned but :cfunc:`PyErr_Occurred` will return false.
.. cfunction:: PyObject* PyObject_GetIter(PyObject *o)
This is equivalent to the Python expression ``iter(o)``. It returns a new
iterator for the object argument, or the object itself if the object is already
an iterator. Raises :exc:`TypeError` and returns *NULL* if the object cannot be
iterated.